As shown in FIGS. 1 and 2, a prior art device for melting a lashing tape of the binding machine is composed of a U-shaped heat conducting piece 11, an electrically conductive loop 12 disposed in the heat conducting piece 11, and a plurality of locating pieces 14 fastened with the heat conducting piece 11 by a plurality of bolts 13. When the binding machine is started, the power source is made available to the heat conducting piece 11 via the electrically conductive loop 12. The heat conducting piece 11 is heated to reach a predetermined temperature capable of melting both ends of a lashing tape at the time when a binding work is done.
Such a prior art heating device as described above is defective in design in that the device is devoid of a means for indicating the precise timing at which the predetermined temperature is attained, and that the device is incapable of interrupting the power source at the time when the predetermined temperature has attained.